The present invention relates to a ceramic electrostatic chuck with built-in heater or, more particularly, to a ceramic electrostatic chuck with built-in heater used in the temperature elevation and lowering step in a semiconductor process.
Where a heater of wound metal wire has been used for heating of a semiconductor wafer in the manufacturing process of semiconductor devices, contamination of the semiconductor wafer with metals may occur. As a solution to this problem, the use of an integral ceramic heater using a thin film of a ceramic as the heat generating body has been proposed (see official publication of Japanese Patent Kokai No. 4-124076). An electrostatic chuck has been used to fix the semiconductor wafer to the heater during heating at reduced atmospheric pressures. The material from which electrostatic chucks are made is increasingly changing from resins to ceramics as the semiconductor processing temperatures rise higher and higher (see official publication of Japanese Patent Kokai No. 52-67353 and official publication of Japanese Patent Kokai No. 59-124140). Recently, a ceramic electrostatic chuck with built-in heater, which is an integral combination of such a ceramic heater and ceramic electrostatic chuck, has also proposed (see official publication of Japanese Patent Kokai No. 4-358074, official publication of Japanese Patent Kokai No. 5-109876 and official publication of Japanese Patent Kokai No. 5-129210).
However, such a ceramic electrostatic chuck with built-in heater basically has a structure in which different kinds of ceramics are bonded together or, for example, a structure in which an electroconductor layer of graphite and an insulating layer of boron nitride are bonded to a substrate of boron nitride. Such structures have the problem that, during repeated temperature elevation and lowering, separation takes place in the bonded parts because of the thermal stress due to the difference in the thermal expansion coefficients of the materials.